1. Field of the Invention
The present invention relates to a method for inkjet printing suitable for preparing identification documents secured against alteration and for preparing graphic displays secured against graffiti.
2. Description of the Related Art
Identification documents are used on a daily basis to prove identity, verify age, access a secure area, evidence driving privileges, cash a check, make payments, access an automated teller machine (ATM), debit an account and so on. Airplane passengers are required to show an identification document (hereafter “ID document”) during check in, security screening, and prior to boarding their flight. Since they play a critical role in today's society, it is essential that ID documents cannot be falsified and are tamperproof.
Identification cards and documents, such as driving licenses, national or government identification cards, bank cards, credit cards, controlled access cards, and smart cards, carry certain items of information which relate to the identity of the bearer. Examples of such information or variable data include name, address, birth date, signature, and photo of the bearer. The ID cards or documents may in addition carry invariant data, i.e., data common to a large number of cards, for example, the name of an employer.
Inkjet printing is very suitable for handling variable data. Also, due to the compactness of inkjet printers, it has become one of the preferred printing techniques for manufacturing ID documents. Inkjet printing can be used to assemble identification cards as disclosed, for example, in U.S. 2005/0042396 (DIGIMARC) using pigmented inkjet inks for printing the variable data, but it is also possible to use inkjet printing to introduce security features. In U.S. Pat. No. 6,837,959 (AGFA), inkjet printing is used to manufacture identification cards containing a watermark revealed by partial impregnation of a UV-curable lacquer into a porous, opaque ink-receiving layer.
Another security measure used in ID documents is the application of a transparent or translucent layer which is difficult or impossible to remove from the surface of the image-receiving layer, thereby sealing the data printed on the image-receiving layer. Such layers can be applied to ID documents using UV-curable liquids as disclosed in EP 0189125 A (INTERLOCK SICHERHEITSSYSTEME) and U.S. Pat. No. 5,614,289 (KONICA).
WO 01/32789 (3M INNOVATIVE PROPERTIES) discloses a cure-on-demand curable ink composition including a homogeneous mixture of at least one of: (a) a compound having 2 reactive silyl groups, and (b) a compound having at least 3 reactive silyl groups; an acid generating catalyst; and a pigment or pigment chip. The inks are improved for curing speed and outdoor weatherability, but nothing is mentioned about their use for preventing falsification of ID documents or graffiti on billboards.
Photocurable inkjet-inks including specific oxetane compounds are disclosed in U.S. 2004/0050292 (KONISHIROKU) and U.S. 2004/0052967 (KONISHIROKU), however both are silent about methods to prevent falsification of ID documents or graffiti on billboards.
EP 1398175 A (AGFA) discloses an information carrier including a rigid sheet or web support; an opaque, porous receiving layer capable of being rendered substantially transparent by penetration by a lacquer, the receiving layer containing a pigment and a binder; an image provided onto and/or in the receiving layer; a cured pattern of a varnish provided onto the receiving layer provided with the image or onto and/or in the receiving layer provided with the image if the varnish is incapable of rendering the receiving layer transparent; and a cured layer of the lacquer provided on the receiving layer provided with the image and the cured pattern of the varnish, the lacquer having rendered the portions of the receiving layer in contact therewith substantially transparent, wherein the cured pattern of the varnish forms an opaque watermark. The patent is silent on measures to prevent falsification of information carriers.
US 2004/0024089 discloses coatings, printing inks, or paint vanishes including at least one epoxypolysiloxane that is modified with an oxyalkylene group and contains, attached to a Si atom, at least one group of the formula —R3-O—(CnH(2n−m)R4mO—)xR5 where the variables and indices are described therein. Methods for improving the slip and release properties or the leveling and wetting properties of a coating are also disclosed, but the application is silent as to methods to prevent falsification of ID documents or graffiti on billboards.
However, the availability of cheap digital printing systems such as inkjet printers also led to a new type of fraudulent action on ID documents. Overprinting and over-labeling of the personalized information, such as the common “photo swap” method, allows easy and fast abuse of a stolen ID-document.
Therefore, it would highly desirable to be able to manufacture ID documents secured against alteration using a simple manufacturing method and a compact apparatus.